A commonly used track for a crawler vehicle is shown in U.S. Pat. No. 3,857,617, in which the shoes are preferably made of elastomeric material, and are supported and connected to one another by a belt of internally reinforced elastomeric material, the elastic reactions of which keep the shoes packed together, even when rotating with respect to one another on engaging the track sprocket and idler wheels, so that, at any point in their travel, the shoes define a succession of continuous arrow-shaped teeth equally spaced along the longitudinal axis and defining continuous arrow-shaped channels in between.
The known track described above is designed to embody the same properties as a V-ribbed agricultural tyre. That is: a low noise level, by virtue of the arrow-shaped teeth gradually contacting the ground, as opposed to the “hammering” effect of a track with conventional shoes with teeth crosswise to the travelling direction; and a marked improvement in detachment and expulsion of clods, which, as is known, when compacted inside the arrow-shaped channels as the arrow-shaped teeth travel over the terrain, may form into a layer clinging firmly to, and so seriously impairing traction of, the track.
In a V-ribbed agricultural tyre, clod expulsion is promoted by the lateral outlets of the arrow-shaped channels, and by elastic deformation of each arrow-shaped channel as it lifts off the tyre-ground contact patch. In the same way, clod expulsion of the track described in U.S. Pat. No. 3,857,617 is promoted by the lateral outlets of the arrow-shaped channels, by elastic deformation of each arrow-shaped channel, caused by elastic deformation of the belt, at the end of the straight portion of track contacting the terrain, and by the shoes rotating with respect to one another along a jagged line about the sprocket and idler wheels.
Experience, however, shows that, clods are not always expelled from the arrow-shaped channels as the flat-running channels round a curved portion of the track, but are substantially always expelled when fractured crosswise inside the channels as the channels round the curve portion.
Unsuccessful crosswise fracturing of the clods has been found to be caused by elastic deformation of the channels generating evenly distributed stress in the clods, which often fails to fracture the clods crosswise. Especially in U.S. Pat. No. 3,857,617 only a small angle θ will become available between the two succeeding shoes to accommodate the change from a generally flat belt configuration to a circular belt configuration as the shoes pass through the footprint. The deflection of the elastomeric shoes through the small angle θ is not sufficient to fracture the clods and to allow them to be removed out of the arrow-shaped channels.